Differential immunocytochemical staining patterns of uroplakin observed on neoplastic and nonneoplastic tissue fragments obtained from upper urinary tract brush specimens

OBJECTIVE: To discern any differences in the distribution of uroplakin expression on neoplastic and nonneoplastic upper urinary tract lesions. STUDY DESIGN: Thirty-seven representative 95% ethanol-fixed direct smears of brush specimens, which were subsequently diagnosed histologically as 10 reactive and 27 transitional cell carcinomas (TCCs), were stained with polyclonal uroplakin antibodies utilizing the avidin-biotin-peroxidase method. In order to ascertain any differences in diagnostic accuracy between conventional cytomorphology and uroplakin immunocytochemical staining, the results were compared to the original final cytologic diagnoses for all 37 cases. RESULTS: The linear staining pattern on the luminal surface of umbrella cells was the dominant pattern expressed on tissue fragments from all 10 reactive lesions. Tissue fragments from low grade TCC demonstrated a weaker and less continuous superficial membrane staining pattern along with a variably intense, diffuse, membranous staining pattern throughout the tumor cell groups. This staining pattern was seen in all 17 (sensitivity = 100%) histologically confirmed low grade TCCs, of which only 13 of the 17 (sensitivity = 76.5%) were diagnosed as TCC on the original final cytology report. Tissue fragments from 10 high grade TCCs lacked the superficial linear staining pattern seen in reactive cell groups. Instead, all 10 high grade TCCs displayed a strong diffuse membrane staining pattern in all the cells in the fragment and also demonstrated microluminal structures within the tumor cell groups. CONCLUSION: The distinctive patterns of uroplakin antigen expression observed in nonneoplastic and neoplastic upper urinary tract lesions in the present study can greatly enhance the accuracy of diagnostic interpretation of upper urinary tract lesions in conventional cytologic specimens.